My first was a crier too, and I totally empathise with the feelings of despair and exhaustion at the sheer relentlessness of it. A couple of things I did; put her in a bouncy chair in front of the washing machine when it was going - although she'd still cry for a bit, I couldn't hear her as much over the sound of the machine (I could see her, she was safe) and sometimes she would get distracted enough for a break in the screaming. It felt like she had a motion detector, so she had to be held and in motion the entire time. I mainly carried her in a papoose, but had to keep swaying, or bouncing up and down. Her crying did settle to normal levels eventually, but at baby groups and the like, she was always the one screaming! Like you, I felt bad taking her places when all she would do was cry, but people kept reassuring me that they didn't mind and that it was bothering me far more than it was bothering them - I didn't believe them at the time, but I do now!
I was very low at around the stage you're at now. I vividly remember being in tears on the phone to my Mum one day and her telling me to take her out in the pram, and not to worry if she cried. It was literally hammering down with rain but I went out and stomped down the canal path for a couple of miles. She was crying when we set off, but after a while I couldn't hear her, because of the rain and it was hard to see her properly because of the rain on the pram cover. When we got home, she was fast asleep and I felt a bit less frantic about it all. From then on, I made sure we left the house each day, even if it was just for a 30 minute walk, and I certainly felt better for it.
I know it's no help now, but my DD's crying really calmed down and by 6 months, she really only cried for 'normal' crying reasons. She's 16 now, and is an excellent sleeper!😁I was terrified to go through it all again when I had DD2, but she was the total opposite; completely chilled out and despite being born when DD1 was nearly 2, DD2 slept through the night before DD1 ever did!